Update getting-started docs.
Update getting-started docs.

binweiwu/lenskit,chrysalag/lenskit,aglne/lenskit,vijayvani/Lenskit,binweiwu/lenskit,kluver/lenskit,vijayvani/Lenskit,amaliujia/lenskit,martinlaz/lenskit,vaibhav345/lenskit,blankazucenalg/lenskit,linjunleo/lenskit,tajinder-txstate/lenskit,vaibhav345/lenskit,aglne/lenskit,vaibhav345/lenskit,tajinder-txstate/lenskit,tajinder-txstate/lenskit,kluver/lenskit,kluver/lenskit,tajinder-txstate/lenskit,kluver/lenskit,martinlaz/lenskit,blankazucenalg/lenskit,amaliujia/lenskit,vaibhav345/lenskit,chrysalag/lenskit,linjunleo/lenskit,kluver/lenskit